Our 7337 tape library is serial # 10-4576B.  I called it in (reference # 31 TP LQ 3)

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                                                               December 9, 2003

Some 7337 things I learned.  See my w3/~jasper/7337Notes.html, which I stole
from http://www.gruftie.net/ibm/tl/techlib/qna/sfam/html/FB/FB5197L.htm.

Tape slots are 0-9 in the front, 10-14 in the back, left-to-right.
The  left-hand tape drive is numbered 116, is drive A, rmt0, SCSI ID 4.
The right-hand tape drive is numbered 117, is drive B, rmt1, SCSI ID 5.

The /dev/smc0 is the "IBM 7337 Tape Medium Changer" and is SCSI ID 6.

IBM has a tapeutil command that can be used to manipulate the tape library.

To load a tape from slot 11 to drive A,
  tapeutil -f/dev/smc0 move -s 11 -d 116

And to put it back, you need to first unload it, then move it back
  tapeutil -f/dev/rmt0 unload             <=== Note this is rmt0, not smc0!
  tapeutil -f/dev/smc0 move -s 116 -d 11

There's also another device associated with the 7337, and that is /dev/lb0.
This is created by going through "smitty devices"
                                 "Tivoli Storage Manager Devices"
                                 "Library/MediumChanger"
                                 "Add a Library/MediumChanger"
There's only one "Library/MediumChanger Type", and that is "ADSM-SCSI-LB".
On reindeer, the 7337 is attached to vscs1 (00-02-01).
The "CONNECTION address" is typically "6,0".
Under the covers, this does the following mkdev command,
  mkdev -c library -t 'ADSM-SCSI-LB' -s 'scsi' -p 'vscsi1' -w '6,0'

Today though, I was getting this error message trying to recreate /dev/lb0:
  Method error (/etc/methods/cfgadsmdd): 0514-047 Cannot access a device.
  cfgadsmdd[get_i]: ioctl SCIO(L)START failed, errno = 22
  cfgadsmdd[inq..]: free dds.
  cfgadsmdd[main ]: error inquiry or building dds,rc=47


But I upgraded AIX to ML11 and reinstalled the latest Atape driver, and then 
above the mkdev command worked, so now I had a /dev/lb0.  But then the power
went out and when it came back, lb0 was gone.  Now when I do the mkdev, I get
a slightly different error message,
  Method error (/etc/methods/cfgadsmdd): 0514-047 Cannot access a device.
  cfgadsmdd[get_i]: ioctl SCIO(L)INQU first call failed, retry if possible, errno = 19
  cfgadsmdd[inq..]: free dds.
  cfgadsmdd[main ]: error inquiry or building dds,rc=47

But later it worked.